Environmental Health Sciences at the University of Arizona has a long-standing reputation for excellence in training Ph.D. and postdoctoral scientists, as evidenced by the fact that many of our graduates are leaders in academia, industry, and government. To this end, our graduate program has evolved from a systems-based toxicology experience to a curriculum in which students are trained to apply state-of-the art techniques to solve mechanisms of environmental toxicity affecting human diseases in various organ systems. The cutting-edge research programs of 30 Training Grant Faculty members are augmented by innovative technologies developed at the University of Arizona in association with the Southwest Environmental Health Sciences and BIO5 Centers. Additionally, translational approaches undertaken by our NIEHS Superfund Program and Dean Carter Binational Center for Environmental Sciences and Toxicology provide an exceptionally stimulating environment for the training of graduate students and postdoctoral fellows. The interactive research of our Training Grant Faculty and our state-of-the-art Facility Cores extend the training environment from a single laboratory-oriented domain to a multidisciplinary experience strongly supportive of collaborative research. Current trainees are now selected through a University-wide competition and the UA Graduate College provides financial support for all first year Ph.D. students through an umbrella recruitment program, providing a large pool of highly qualified candidates for competitive selection of predoctoral trainees. Predoctoral training is achieved through a combination of coursework, laboratory research, and supplemental enrichment activities. Postdoctoral trainees participate in innovative research programs and are guided to develop professional skills in oral and written communication and leadership. Over the past five years, our curricular changes have paralleled the evolving expertise of the Training Grant Faculty. We have recruited eight senior full Professors, three Associate Professors, and seven junior Assistant Professors into the Training Grant, which significantly enhanced our core strengths in mechanistic-based molecular toxicology training. The request for continuation of NIEHS support is justified by the highly successful nature of our program, the clear demand for our graduates, the strong emphasis we place on leadership skills for our trainees and postdoctoral fellows, the increasing number of students interested in toxicology and environmental health, substantial institutional commitment, the strong and well- funded research programs of our faculty, and the excellence of the training environment.